The present invention relates generally to the field of image forming apparatuses and in particular to a photoconductive member biased to an operating voltage and electrically isolated from a mounting shaft.
A variety of elements within an electrophotographic image forming apparatus operate at relatively high operating voltages. These voltages are used, for example, to pre-charge a photoconductive member to allow a latent image to be optically formed thereon; to transfer electrically and/or magnetically charged toner particles to the photoconductive member to develop the latent image; and to transfer the developed image from the photoconductive member to a media sheet. Where possible, it is preferable to isolate these voltages to specific operational elements, to reduce the risk of short circuit or electrocution. For example, an operating voltage applied to a photoconductive member is preferably restricted to the photoconductive member itself, and isolated from a metallic housing to which the photoconductive member is mounted.
Electrical isolation of various components has traditionally been addressed in the design of removable cartridges in which the components are mounted. For example, a typical prior art electrophotographic image forming apparatus may include one or more removable cartridges, each cartridge containing a reservoir holding a supply of toner, a photoconductive drum for optically forming a latent image and developing the image with the toner, and a developer roller for applying the toner to the photoconductive drum. The image removable cartridge may additionally include various rollers, paddles, augers and blades, as well known in the art. One or more electrical contacts on the cartridge accept an operating voltage, and transfer it to the appropriate component(s).
A recent development in the state of the art of electrophotography is the separation of many components traditionally CaCO-located in a single removable container into separate units. In some cases, the components may be mounted to a moveable subunit such as a door, and removed from their operational position whenever the subunit is opened. This requires the provision of precise positioning means, so that the components are returned to a precise operating position each time the subunit is mated to the main housing. One well-known way to repeatedly, precisely locate a cylindrical component is to provide V-shaped receiving voids in a rigid frame, into which fit metallic bearings supporting a shaft that runs through the axis of the cylindrical component. In the event that the cylindrical component must be biased to a high operating voltage, however, prior-art electrical contacts would simultaneously bias the conductive shaft to the operating voltage. This may present an unacceptable hazard where the conductive shaft mounts via conductive bearings to a conductive machine frame.